Comparison between qualitative and real-time polymerase chain reaction to evaluate minimal residual disease in children with acute lymphoblastic leukemia

Introduction:

Minimal residual disease is an important independent prognostic factor that can identify poor responders among patients with acute lymphoblastic leukemia.

Seventy-four patients diagnosed with acute lymphoblastic leukemia were enrolled. Minimal residual disease was evaluated by qualitative polymerase chain reaction in 57 and by both tests in 44. The Kaplan-Meier and multivariate Cox methods and the log-rank test were used for statistical analysis.

Nine patients (15.8%) were positive for minimal residual disease by qualitative polymerase chain reaction and 11 (25%) by real-time polymerase chain reaction considering a cut-off point of 1 × 10−3 for precursor B-cell acute lymphoblastic leukemia and 1 × 10−2 for T-cell acute lymphoblastic leukemia. Using the qualitative method, the 3.5-year leukemia- free survival was signiﬁcantly higher in children negative for minimal residual disease compared to those with positive results (84.1% ± 5.6% versus 41.7% ± 17.3%, respectively; p-value = 0.004). There was no signiﬁcant association between leukemia-free survival and minimal residual disease by real-time polymerase chain reaction. Minimal residual disease by qualitative polymerase chain reaction was the only variable signiﬁcantly correlated to leukemia-free survival.

Given the difﬁculties in the implementation of minimal residual disease monitoring by real-time polymerase chain reaction in most treatment centers in Brazil, the qualitative polymerase chain reaction strategy may be a cost-effective alternative.